<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>棋盘</title>
</head>
<body>
    <div id="container">
        <div></div>
        <div>x</div>
    </div>
</body>
<style>
    #container{

        background: antiquewhite;
    }
    #container:nth-child(odd)
    {
        width: 55px;
        height: 55px;
        background: burlywood;
    }
    #container:nth-child(even)
    {
        width: 55px;
        height: 55px;
        background: aquamarine;
    }
</style>
</html>